3.1. Field of the Invention
The present invention relates to a reaction chamber assembly that includes outer walls enclosing an outer volume such as an oven structure and a removable liner enclosing a reaction chamber installed into the outer chamber to substantially contain reactants inside the reaction chamber thereby preventing the outer walls from being contaminated by reactants. The removable liner can be removed from the outer volume when it is contaminated by reactants and replaced. Preferably, the removable liner can be cleaned or decontaminated and reused.
3.2. The Related Art
Reaction chambers such as gas deposition chambers can become contaminated with reactants and or reactant byproducts. This may occur over prolonged use wherein reactants introduced into the reaction chamber react with internal walls thereof and with other elements inside the reaction chamber and build up extensive coating layers or contaminants on the internal walls and the other elements, rendering them unusable. Over time, contaminant build up on the internal walls may begin to crack and peel causing substrate coating failures. Other failures due to contaminant build up include sensor failure, reduced wall and substrate temperatures, or increases in thermal cycling times and concerns for human safety. In production environments, the reaction chamber is typically broken down and cleaned or replaced on a regular maintenance schedule, which may be based on the number of coating cycles performed and which may vary according to the type of reactants being used. While such cleaning occurrences are predictable and can be planned for, they nonetheless disrupt production cycles.
Unscheduled cleaning or maintenance events may occur when a deposition chamber becomes accidently contaminated by a hazardous material and needs to be decontaminated immediately for human safety reasons. In these cases, the cleaning or decontamination is unexpected and may be very disruptive to a production cycle. Accordingly, there is a need in the art for a faster solution for decontaminating a reaction chamber.
Cook et al. in U.S. Pat. Appl. Pub. No. 2005/0188923, suggests that an ex situ cleaning approach can be used to clean a chamber by disassembling the chamber and cleaning the chamber parts by etching them in an acid bath or the like. However, the ex situ method is undesirable because of the excessive time required to disassemble, clean and reassemble the chamber. Cook et al. further suggests an in situ cleaning method wherein an etching gas is pumped into the chamber to etch material layers from internal surfaces of the chamber. However the in situ cleaning method is undesirable because the etch rate is slow, because the etching gas is corrosive and otherwise hazardous, e.g. a hazard to human safety, and because the etching gas may remain in the chamber and contaminate future substrate coating cycles. Cool et al. suggest a third approach for cleaning the chamber, which is to configure one or more removable liners that cover the chamber wall and that the liner may be removed and cleaned or replaced, avoiding extensive cleaning of the other chamber hardware. However, beyond recommending materials for the liner, Cook et al. does not disclose a liner structure of any kind and is completely silent about how the reactants can be contained within the one or more removable liners covering the chamber walls in order prevent the chamber walls from becoming contaminated.
Some reaction chambers are pumped down to a low, medium, or high vacuum pressure (less than 760 torr to about 10 micro torr). The pump down cycle removes air, water vapor, and other gases from the reaction chamber before introducing reactants to ensure that only a desired reactant is present in the chamber during a coating cycle. Additionally, the pump down cycle establishes a chamber vacuum pressure that enhances the desired thin film formation. A pump down or purge cycle is again performed after each reactant has been introduced to remove the reactant from the chamber. Pumping down the chamber provides an added benefit in that it creates a high pressure gradient across the reaction chamber walls and this serves to prevent reactants from leaking through the chamber walls but may cause contaminates to leak through the chamber walls form outside the reaction chamber. When a liner is introduced into the reaction chamber, as suggested by Cook et al., there is no high pressure gradient across that liner wall since the entire chamber, including the liner, is substantially at the same gas pressure. An effective liner needs to contain reactants therein in order to prevent the reactants from contaminating the chamber walls and this containment is made more difficult without the benefit of a high pressure gradient across the liner wall. One solution for preventing corrosive gas from reaching electrical elements housed inside a reaction chamber is disclosed in U.S. Pat. No. 7,015,426 by Doering et al. entitled PURGED HEATER-SUSCEPTOR FOR AN ADL/CVD REACTOR wherein corrosive elements, e.g. conductive wires and the like, disposed inside the gas chamber, are enclosed by a hollow sleeve and a flow of purge gas is continuously passed through the hollow sleeve. The purge gas flowing through the hollow sleeve surrounds the corrosive elements thereby isolating the corrosive elements from the process gasses inside the chamber. The purge gas is allowed to pass from the hollow sleeve into the chamber to mix with the process gas and to be exhausted out of the chamber with the process gasses. While the solution proposed by Doering at al. isolates conductive elements inside the chamber from exposure to process gasses Doering et al. is completely silent about containing reactants inside a removable liner by creating a pressure gradient across the walls of the removable liner by introducing a purge gas flow to surround the removable liner.
More generally, there is a need in the art to increase the size of reaction chambers to handle larger substrates. There is a further need in the art to increase coating throughput by providing reaction chambers suited for batch coating cycles. There is a still further need in the art, to decrease scheduled or unscheduled down time of production oriented reaction chamber systems by providing a reaction chamber that can be easily and quickly decontaminated.